Spencer S-12 Air Car was designed by P.H. Spencer.  The first Air Car was drawn in 1939/1940, built in 1941 and sold to Republic Aviation.  The design was converted to metal and named "The Republic Sea Bee."  Production was delayed until 1945 due to WWII.
Spence redesigned the Air Car in 1967 so as to facilitate the construction of the aircraft by amateurs or homebuilders.  The prototype of this configuration was N111DA, owned by Col. Dale Anderson.  The first effort had a 180hp engine and was flown to Oshkosh twice, but was upgraded to 200hp, 220hp 260hp, 285, and 300hp at the request of builders wanting more payload and performance.